In recent years, with the development of portable devices such as personal computers and cellular phones as well as hybrid vehicles, electric vehicles and the like, there is an increasing demand for secondary batteries (particularly lithium secondary batteries) as their power supplies.
It is known that a foil-shaped aluminum base is used as the current collector for electrodes (hereinafter referred to simply as “current collector”) that may be used in the positive electrode or the negative electrode of such a secondary battery.
It is known that a low adhesion of the current collector to a layer containing an active material (hereinafter also referred to as “active material layer”) in the positive electrode or the negative electrode of the second battery causes the active material to come off the current collector during charge/discharge to adversely affect the battery characteristics.
Techniques for roughening the surfaces of aluminum bases have been proposed in order to improve the adhesion between current collectors and active materials (see, for example, JP 11-16575 A, JP 2003-51313 A, JP 2005-2371 A, JP 2008-10419 A and JP 2008-282797 A).